Exporting isocontour data from 2D contour plot (radiation pattern)

Hi,

I would like to export a single contour line data from 2D contour plot.
I need to export an isocontor of a given level in the radiation pattern of an antenna (e.g. -3 dB).
I need data like the one generated by Matlab's contour function (or in similar format).

Is that possible at all?

I will be very grateful for your prompt reply.

I need to use the data in my publication in IEEE- (a rewiever reqqiest).

Thank you in advance.

Piotr.